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How to Calculate Unfolding Dimensions in Sheet Metal Manufacturing
Category：answer Publishing time：2025-10-17 05:47:20 Browse： Times
In the sheet metal processing industry, the calculation of unfolding dimensions is a crucial link. It directly affects the material utilization rate, processing accuracy, and the quality of the final product. The so-called 'unfolding dimensions' refer to the total size of all surfaces when a three-dimensional bent sheet metal part is unfolded into a two-dimensional plane state. Accurate calculation of unfolding dimensions can not only reduce material waste but also improve production efficiency and product quality.
Basic Principles of Unfolding Dimensions
In the bending process of sheet metal parts, due to the plastic deformation characteristics of the material, the inner side is compressed while the outer side is stretched. Between these two layers, there exists a 'neutral layer', which maintains its length basically unchanged during the bending process. Therefore, the calculation of the unfolding length is based on the neutral layer.
The general formula for unfolding size is:
> Unfolding length = sum of straight line lengths + bending compensation value
Among them, the 'bending compensation value' is usually represented by 'K factor' or 'bending deduction', and the specific value depends on factors such as material type, plate thickness, mold shape, and bending angle.
Second, commonly used unfolding calculation methods
1. Empirical formula method
In actual production, many enterprises will establish a set of bending parameter table according to their own experience. For example, for different angles and materials of bending, record their actual unfolding size. Although this method is simple and practical, it lacks versatility.
2. K factor method
The K factor is the ratio of the position of the neutral layer to the material thickness (K = t / T, where t is the distance from the neutral layer to the inner surface, and T is the material thickness).
The calculation formula for unfolding length is:
> Unfolding length = straight edge length + π × (R + K×T) × (θ / 180)
Among them, R is the bending inner radius, and θ is the bending angle.
3. Bend deduction method (Bend Deduction)
Bend deduction method is to obtain the material springback amount at the bending part through actual measurement or table lookup, thereby deducting this part of length from the theoretical length. It is suitable for unfolding calculation of complex parts.
4. Software automatic unfolding
Modern CAD/CAM software such as SolidWorks, AutoCAD Inventor, Pro/E, etc., all have automatic unfolding functions. After entering material parameters, bending radius, and angle, the software will automatically generate unfolding dimensions, greatly improving efficiency and accuracy.
Three, Factors affecting the unfolding size
1. Material type: Different materials have different ductility, such as stainless steel, aluminum, and cold-rolled steel plates have different K factors.
2. Plate thickness: The thicker the plate, the more obvious the neutral layer offset, and the K factor needs to be adjusted.
3. Bending method: Different processes such as air bending, bottom pressure bending, and pressure bending have different degrees of material deformation.
4. Molding size: The size of the lower mold opening directly affects the bending inner radius, thereby affecting the unfolding size.
Four, Matters needing attention in practical application
- Trial folding verification: Before mass production, it is recommended to carry out a trial folding first, measure the actual unfolding length, and correct the theoretical calculation value.
- Springback compensation: Especially in high-precision parts, it is necessary to consider the influence of material springback on dimensions.
- Unified parameter standards: For commonly used materials and processes, establish a unified parameter database for easy subsequent quick access.
Five, Conclusion
Accurate calculation of the unfolding dimensions is one of the key technologies in sheet metal manufacturing. It not only affects the forming accuracy of parts but also directly relates to the production cost and efficiency of enterprises. With the development of digital manufacturing technology, more and more enterprises are beginning to use software for automatic unfolding design, but still need to optimize the parameter settings with practical experience. Mastering scientific unfolding methods is an important way to improve the level of sheet metal processing.
In the sheet metal processing industry, the calculation of unfolding dimensions is a crucial link. It directly affects the material utilization rate, processing accuracy, and the quality of the final product. The so-called 'unfolding dimensions' refer to the total size of all surfaces when a three-dimensional bent sheet metal part is unfolded into a two-dimensional plane state. Accurate calculation of unfolding dimensions can not only reduce material waste but also improve production efficiency and product quality.
Basic Principles of Unfolding Dimensions
In the bending process of sheet metal parts, due to the plastic deformation characteristics of the material, the inner side is compressed while the outer side is stretched. Between these two layers, there exists a 'neutral layer', which maintains its length basically unchanged during the bending process. Therefore, the calculation of the unfolding length is based on the neutral layer.
The general formula for unfolding size is:
> Unfolding length = sum of straight line lengths + bending compensation value
Among them, the 'bending compensation value' is usually represented by 'K factor' or 'bending deduction', and the specific value depends on factors such as material type, plate thickness, mold shape, and bending angle.
Second, commonly used unfolding calculation methods
1. Empirical formula method
In actual production, many enterprises will establish a set of bending parameter table according to their own experience. For example, for different angles and materials of bending, record their actual unfolding size. Although this method is simple and practical, it lacks versatility.
2. K factor method
The K factor is the ratio of the position of the neutral layer to the material thickness (K = t / T, where t is the distance from the neutral layer to the inner surface, and T is the material thickness).
The calculation formula for unfolding length is:
> Unfolding length = straight edge length + π × (R + K×T) × (θ / 180)
Among them, R is the bending inner radius, and θ is the bending angle.
3. Bend deduction method (Bend Deduction)
Bend deduction method is to obtain the material springback amount at the bending part through actual measurement or table lookup, thereby deducting this part of length from the theoretical length. It is suitable for unfolding calculation of complex parts.
4. Software automatic unfolding
Modern CAD/CAM software such as SolidWorks, AutoCAD Inventor, Pro/E, etc., all have automatic unfolding functions. After entering material parameters, bending radius, and angle, the software will automatically generate unfolding dimensions, greatly improving efficiency and accuracy.
Three, Factors affecting the unfolding size
1. Material type: Different materials have different ductility, such as stainless steel, aluminum, and cold-rolled steel plates have different K factors.
2. Plate thickness: The thicker the plate, the more obvious the neutral layer offset, and the K factor needs to be adjusted.
3. Bending method: Different processes such as air bending, bottom pressure bending, and pressure bending have different degrees of material deformation.
4. Molding size: The size of the lower mold opening directly affects the bending inner radius, thereby affecting the unfolding size.
Four, Matters needing attention in practical application
- Trial folding verification: Before mass production, it is recommended to carry out a trial folding first, measure the actual unfolding length, and correct the theoretical calculation value.
- Springback compensation: Especially in high-precision parts, it is necessary to consider the influence of material springback on dimensions.
- Unified parameter standards: For commonly used materials and processes, establish a unified parameter database for easy subsequent quick access.
Five, Conclusion
Accurate calculation of the unfolding dimensions is one of the key technologies in sheet metal manufacturing. It not only affects the forming accuracy of parts but also directly relates to the production cost and efficiency of enterprises. With the development of digital manufacturing technology, more and more enterprises are beginning to use software for automatic unfolding design, but still need to optimize the parameter settings with practical experience. Mastering scientific unfolding methods is an important way to improve the level of sheet metal processing.
